Combined Approved Plans RAL21/0003

                Total Concept Homes                                                                                          20332-001-Rev1
                                                                                                                              22 March 2021

                Table 2: Details of Qualitative Risk Assessment for Property (AGS 2007
                                                                                 Assessed
                  Hazard                            Likelihood   Consequence
                                                                                   Risk
                                                                                            Comments

                                                                                            The driveway alignment exploits an existing track in
                                                                                            some parts, and although the central portion of the
                                                                                            driveway is proposed sidelong to a moderately
                                                                                            steep slope; given the presence of stiff to very stiff
                                                                                            residual soils and XW materials from surface, no
                  1: Proposed driveway -                                                    evidence of existing instability (including relatively
                 shallow failure through existing                                           good performance of existing fill embankments),
                 natural soil materials (fill        Unlikely       Minor             Low   apparent lack of shallow groundwater, and the
                 subgrades or earthworks cuts);                                             proposed engineer designed retention of future fill
                 or future fill materials                                                   for the driveway, it is considered Unlikely that a
                                                                                            landslip would develop, subject to implementation of
                                                                                            the recommendations in Section 4 (e.g. foundations
                                                                                            levels and fill quality). Given a potential Medium
                                                                                            impact from such shallow instability the resultant risk
                                                                                            would be Low as per AGS 2007.


                                                                                            Given the presence of stiff residual soils at surface,
                                                                                            and stiff to very stiff XW materials below at shallow
                                                                                            depth, the rounded nature of the spur crest where
                                                                                            construction is proposed, and negligible catchment
                  2: Proposed residence on
                                                                                            for water above the site and apparent lack of
                 subdivided Lot - Failure
                                                                                            groundwater, and no evidence of existing instability
                 through natural soils or XW         Unlikely      Medium             Low
                                                                                            in the vicinity of the proposed residence, it is
                 materials above the foundation
                                                                                            considered Unlikely that a landslip would develop,
                 depth
                                                                                            subject to implementation of the recommendations
                                                                                            in Section 4. With a potential Medium impact from
                                                                                            such shallow instability the resultant risk would be
                                                                                            Low as per AGS 2007.



                                                                                            The likelihood of a deep failure through the weathered
                                                                                            phyllite rock below the foundation depth is assessed
                  3: Proposed residence on
                                                                                            as Barely Credible due to the strength of these
                 subdivided Lot, or proposed
                                                     Barely                                 materials, no evidence of existing instability, and
                 driveway alignment - Deep                          Major        Very Low
                                                    Credible                                relatively consistent nature of the sloping ground
                 seated failure in weathered rock
                                                                                            across the development area. Although the
                 below the foundation depth
                                                                                            consequence of such a failure could be Major, the
                                                                                            resultant risk is Very Low as per AGS 2007.




                The potential impacts on slope stability of the development components have been assessed, and the
                measures recommended below in Section 4 have been designed to mitigate those impacts.

                3.2.1 Effluent Disposal
                Ground Drill has prepared an effluent disposal report (Ref. Job No. 20/373-2, dated 22 March 2021). The
                indicative proposed effluent disposal area is located to the east of the proposed building area, as illustrated in
                the Ground Drill report, which is attached at the end of this letter. This area is considered acceptable from a
                slope stability point of view. Should the proposed effluent disposal area be moved, Tectonic must be notified
                to re-assess the impacts on slope stability.

                Ground Drill has recommended application rate of 3 mm/day using a covered surface irrigation system.
                Considering this application rate compared with the trigger levels required for the occurrence of a landslide in
                this setting (e.g. a severe rain event), the effect of the irrigation on slope stability would be considered
                minimal. Nevertheless, it is recommended that the land application area be revegetated as soon as possible.
                Vegetation should include native species which are used for stabilisation of steep slopes and suitable for wet
                soils with high nutrient loads (e.g. Lomandra).
                The on-site effluent disposal system must be located a suitable distance away from any watercourse,
                dwellings and recreation areas. Setback distances are subject to the level of treatment proposed and shall
                be in accordance with Local and State Government requirements.




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Document Set ID: 21426326
Version: 1, Version Date: 24/03/2021